Frequently asked questions – Static IP addresses

Have questions about static IP addresses? Check out the top FAQs. 

What is an IP address?

Devices on the internet use IP addresses to locate and talk to each other on the internet, much the same way people use phone numbers to call someone, street addresses for sending mail, and e-mail addresses to send electronic messages to a specific person. There are two kinds of IP addresses: static and dynamic.

What is the difference between a dynamic IP and a static IP?

A dynamic IP changes. A static IP does not change.

Why would I need a static IP address?

So that your public IP address will not change. You may want to consider a static IP address if you:

  • Have a server on your network that requires external access [E-mail, FTP, Web].
  • Run a service or application that requires external access [Security System, Video or Audio services].
  • Don't want your IP address to change for any reason [VPN, IP-PBX].
What is the difference between a single static IP lease and a block lease?

If you lease a single static IP address, it only provides a public IP address to the modem. If you need a public IP address on a device behind your internet modem, you will need to lease a block of IP addresses.

What is the difference between how many static IP addresses I lease and how many can be assigned?

When you lease a block of IP addresses, three IP addresses are reserved for routing. The other IP addresses can be assigned to devices behind your DSL modem.

What are the costs associated with static IPs?

Go to the article How do I order or cancel static IP(s) for pricing.

In what scenario's could I lose my static IP addresses with CenturyLink?

You can lose your Static IP(s) in the following scenarios:

  • Moving or modifying your service
  • Changing your ISP, your speed or any change to your IP block size
  • There are other scenarios where a change in assigned IP addresses may be required at the discretion of CenturyLink. CenturyLink will make its best effort to notify you in advance when this is necessary.
If I move my service, what happens to my static IP(s)?

When you call CenturyLink to move your services, let us know that you have a "static IP lease", and that you want to keep them. At that time, we'll see if your current static IP(s) can be moved to your new location.

If I change my ISP, what happens to my static IP(s)?

If you change your ISP, you will lose your static IP(s).

What is ARIN?

ARIN (American Registry for Internet Numbers) is a nonprofit corporation that manages the distribution of IP addresses for most of North America. (For additional information see

Why should I register my static IPs with ARIN?

Registering your static IPs with ARIN is a good idea because it:

  • Avoids duplicate distribution
  • Ensures traffic routing
What is DNS?

DNS (Domain Name System) is a directory that translates names to numbers. It is like a phone book for the internet. DNS translates a domain name (e.g. to the internet IP address at which the web site with that domain name is hosted (e.g. Without DNS, you would need to know the IP address to get to a specific web site. However, DNS 'looks up' the address typed in to the address bar and translates it to the IP address for you, so the appropriate web page can be found and displayed.

What is reverse DNS?

Reverse DNS (rDNS) is the opposite directory from DNS. It translates numbers to names. rDNS translates an IP address to a domain name. The original use of the rDNS was mainly for network troubleshooting. More recently rDNS has been used as an anti-spam technique.

Some email servers may view email as spam if it originates from an IP address that does not have rDNS configured. In more extreme situations, the receiving email server will compare the originating IP address, the domain name that is listed as the sender, and then check for a rDNS record pointing back to the sender's domain name.

Do I need to order something special to get IPv6?

No. For more information go to the IPv6 FAQs page.

What are the CenturyLink IPv4 DNS resolvers?

Go to the CenturyLink DNS page.

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